The variety of distribution in accordance with recent diversity of diet and lifestyle has diversified forms of foods containing gelatinized starch. In the case of rice diet such as “hakuhan” (plain cooked rice), “sekihan” (red-bean rice), “okowa” (steamed glutinous rice), “sushi” (vinegared rice diet), “ajituke-meshi” (seasoned rice), “onigiri” (rice ball), “ohagi” (bean cake), “mochi” (rice cake), and there processed food, noodles such as “udon” (Japanese wheat noodle), “soba” (buckwheat noodle), Chinese noodle, spaghetti, “gyoza” (Chinese steam-baked meat pie), “shumai” (Chinese steamed meat dumpling), the demand for them packaged for a one feed or in a retort pouch have grown with the practical distribution and storage under a room, refrigerated, chilled, or frozen temperature, and with the applicability to fuss-free home cooking.
However, because of the relatively high moisture content, foods containing gelatinized starch deteriorate in eating-quality characteristics with the increase of hardness and the decrease of stickiness resulting from retrogradation of the starch and the increase of unpleasant smells resulting from oxidized lipid according to the storage period.
Several methods for keeping the eating-quality characteristics of foods containing gelatinized starch are proposed using enzymes such as amylases, saccharides such as oligosaccharides or sugar alcohols thereof, surfactants such as sucrose-fatty acid esters or glycerol-fatty acid esters, proteins such as gelatin, and polysaccharides in the preparation process. However, the above methods still remain the following problem such as the insufficient keeping-effect for the eating-quality characteristics, the deterioration of characteristics such as flavor, color, or other properties of a rice diet, and the complicated process. Therefore, improvements in a preparation technology of foods containing gelatinized starch are desired to keep the eating-quality characteristics for a long time in accordance with their distribution.
Some methods with rectified above defects are proposed; such as a method for preparing noodles in which the cooking water, cooling water thereafter, or liquid preparation for the boiled noodle are admixed with saccharides (for example, Japanese Patent Kokai No. 196225/96), and for keeping the eating-quality characteristics of rice diets or the frozen ones by boiling with trehalose (for example, Japanese Patent Kokai Nos. 147916/95, 206006/97, 262581/98, and 116346/00). But in the case of foods containing gelatinized starch heated with trehalose, the saccharide may not sufficiently permeate into the foods resulting in uneven hardness or the following acceleration thereof by the inhibited gelatinization. Particularly, the softness of rice diets may not be kept when stored under chilled or refrigerated conditions. According to Japanese Paten Kokai 147916/95, the addition of trehalose to rice diets after cooked is not suitable because of the low dispersibility and insufficient effect.